Referring to the drawings, known mechanical pencils, similar to that shown in FIG. 1 are constructed so that knocking hammer 3 is moved up and down by swinging or shaking the outer sleeve 1. A chuck 4, part of lead holder 2 is opened or shut against the force of chuck-clamping spring 5 by moving the knocking hammer 3 up and down so that lead can be extended by a given length from a head member 6 connected with the outer sleeve 1. In the above known construction, the spring force of chuck-clamping spring 5 is weakened, because if the spring force is too strong, opening of the chuck by knocking hammer 3 cannot be efficiently or positively performed. However, when the spring force is weak, allowing the opening operation to be successfully performed the shutting operation of the chuck cannot be efficiently performed, so that slipping of the lead can occur when writing. Thus writing with this type of mechanical pencil can be difficult.
Another known mechanical swing-type mechanical pencil similar to the embodiment of FIG. 2 has a knocking hammer 111 reciprocated in an axial direction by softly swinging the pencil sleeve 108 knocking lead holding pipe 101 of lead feeding mechanism 107 so that chuck 102 can open or shut.
Chuck 102 inserted in chuck ring 103 is retained on the forward end of chuck ring bearing sleeve 104, inserted in the lead pipe through a chuck coupling and can be moved against the force of a chuck clamping springly by the above-mentioned knocking, to open chuck 104 so that lead can be extended from a head member 109.
However, in the above-mentioned known constructions, lead pipe 101 is provided with a stopper and with a chuck coupling contacts the forward and rear ends of the knocking hammer 111 to restrain the scope of movement of the knocking hammer. The inside of the outer sleeve 108 is provided with a stopper on the outer sleeve retaining a stopper on the pipe to limit the scope of the movement of knocking hammer 111. A total of three parts of a chuck coupling and stoppers on the pipe and on the outer sleeve are required. This is a problem because the construction is complicated, and assembly is not easy.
Still another swing-type mechanical pencil, similar to FIG. 5 has knocking hammer 202 reciprocating (up and down) in an axial direction by swinging an outer sleeve 201 to knock lead case 205 of lead-feeding mechanism 203. Chuck 19 inserted in chuck ring 218 retained on the forward portion of chuck ring bearing sleeve 217, sets the forward end portion of lead case 205 and can be moved against the spring force of a chuck-clamping spring 220 by the above-mentioned knocking, so the chuck can be opened or shut. Thereby, lead can be fed by a given length from chuck 219, and be sent out from head pipe 223 of guide 222 in the forward end portion of the head member 221 attached to outer sleeve 201.
Further, lead 204 can be drawn, together with the head pipe 223, into head member 221 by pushing the end of the lead while maintaining an opened state of chuck 219. It is possible to extend lead by pushing lead case 205 by knocking its rear end.
However, in the above-mentioned construction a retaining part for restraining knocking hammer 202 from moving upward is needed besides a projecting part 224 serving also as a bearing for spring 220 at the outer surface of lead case 205. Because lead case 205 can be knocked by knocking hammer 202 moving upward, there is a problem of an unexpected extension of lead performed by the upward and downward movement of the outer member caused by the mechanical pencil being vibrated while being carried.
In known swing-type mechanical pencils similar to that shown in FIG. 9, a knocking hammer 302 can be reciprocated (moved up and down) in an axial direction by swinging outer sleeve 301 and knocking lead case 305 of lead-feeding mechanism 303. Chuck 319 inserted in chuck ring 318 is retained on the forward portion of chuck ring bearing sleeve 317, set in the forward end portion of lead case 305 and can be moved against the spring force of a chuck-clamping spring 320 by the above-mentioned knocking. The chuck can thereby be opened or shut, and lead fed by a given length from chuck 319, and extended from head pipe 823 of slider guide 322 in the forward end portion of head member 321 attached to outer sleeve 301.
Further, lead 304 can be drawn with the head pipe Into head member 321 by pushing the end of the lead while maintaining an opened position of chuck 319. It is also possible to extend lead by pushing on lead case 305 by knocking the rear end.
However, in the above-mentioned known construction there is the problem of lead being positively held, as it does not have a construction allowing upward movement of hammer 302 to male lead case 305 move up compulsorily to shut chuck 319. Further, as lead case 305 is knocked by upward and downward movement of the knocking hammer, there is another problem of an expected extension of lead caused by the upward and downward vibration of the pencil while being carried.